How to mock Tedious Module SQL Connection functions in JEST - jestjs

Question

I am using Azure functions written in Nodejs.
I have logic to insert into DB after all actions are completed. This gets called from main index.js after some api calls. So, from test class im expecting to mock database methods. and cant understand mocking much!
Below is the code for Database logic.
'use strict';
const { Connection, Request, TYPES } = require('tedious');
const config = {
server: process.env.myDB_Server,
authentication: {
type: 'default',
options: {
userName: process.env.myDB_User,
password: process.env.myDB_Pwd
}
},
options: {
encrypt: true,
database: process.env.myDB_Name
}
};
const myDB = process.env.myDB;
module.exports = async(context, myPayload, last_Modified_By, status, errorCode, errorMsg, errorDescription) => {
try {
context.log('inside azureTable function');
let connection = new Connection(config);
connection.on('connect', function(err1) {
if (err1) {
context.log('Error connection.OnConnect to DB:::', err1.message);
//logger.error('Error connection.OnConnect to DB::', err1);
let dbStatus = {};
dbStatus["status"] = 400;
dbStatus["message"] = err1.message;
context.res.body["dbStatus"] = dbStatus;
context.done();
} else {
context.log('Database Connection Successful.');
var request = new Request("INSERT INTO " + myDB + " (Correlation_Id,Created_Date,LastModified_Date,Last_Modified_By,Status_CD,Error_Code,Error_Msg,Error_Description,Payload) VALUES (#correlationId,CURRENT_TIMESTAMP,CURRENT_TIMESTAMP,#Last_Modified_By,#Status_CD,#Error_Code,#Error_Msg,#Error_Description,#Payload);", function(err2) {
if (err2) {
context.log('Error inserting records to DB::', err2.message);
//logger.error('Error inserting records to DB::' + err2.message);
let dbStatus = {};
dbStatus["status"] = 400;
dbStatus["message"] = err2.message;
context.res.body["dbStatus"] = dbStatus;
context.done();
}
});
request.addParameter('correlationId', TYPES.NVarChar, JSON.parse(myPayload).correlationId);
request.addParameter('Last_Modified_By', TYPES.NVarChar, last_Modified_By);
request.addParameter('Status_CD', TYPES.NVarChar, status);
request.addParameter('Error_Code', TYPES.Int, errorCode);
request.addParameter('Error_Msg', TYPES.NVarChar, errorMsg);
request.addParameter('Error_Description', TYPES.NVarChar, errorDescription);
request.addParameter('Payload', TYPES.NVarChar, myPayload);
// Close the connection after the final event emitted by the request, after the callback passes
request.on("requestCompleted", function(rowCount, more) {
context.log('Records Successfully inserted into DB');
connection.close();
let dbStatus = {};
dbStatus["status"] = 201;
dbStatus["message"] = "Records Successfully inserted into DB";
context.res.body["dbStatus"] = dbStatus;
context.done();
});
connection.execSql(request);
}
});
connection.connect();
} catch (err) {
context.log('Error in main function::', err.message);
//logger.error('Error in main function::' + err.message);
let dbStatus = {};
dbStatus["status"] = 400;
dbStatus["message"] = err.message;
context.res.body["dbStatus"] = dbStatus;
context.done();
}
};
How can i mock the connection.on connect or request = new Request without actually hitting DB ?
I tried this, but its going to actual connection.
index.test.js
test('return 500 when db connection fails" ', async() => {
const tedious = require('tedious');
const connectionMock = jest.spyOn(tedious, 'connect');
connectionMock.mockImplementation(() => {
return {
}
});
//calling index js
}, 15000);
test('return 500 when db connection fails" ', async() => {
const tedious = require('tedious');
const connectionMock = jest.spyOn(tedious, 'Connection');
connectionMock.mockImplementation(() => {
{
throw new Error('some err');
}
});
//calling index js
}, 15000);
After going through some docs, tried below with no luck. Jest is not setting return value and gets timed out.
jest.mock('tedious', () => ({
Connection: jest.fn(() => ({
connect: jest.fn().mockReturnValue('err'),
on: jest.fn().mockReturnValue('err')
}))
}))
/* jest.mock('tedious', () => ({
Connection: jest.fn(() => ({
connect: jest.fn(() => (connect, cb) => cb(null)),
on: jest.fn(() => (connect, cb) => cb('err'))
}))
})) */

Answer 1

Finally I figured it out.
Issue was the mocking params not being set correctly. Unnecessarily used Jest.fn() for inner methods which actually doesn't help.
Here is the final solution:
jest.mock('tedious', () => ({
Connection: jest.fn(() => ({
connect: () => {},
on: (connect, cb) => cb(),
close: () => {},
execSql: () => {}
})),
TYPES: jest.fn(),
Request: jest.fn(() => ({
constructor: (sqlString, cb) => cb('err', null, null),
addParameter: (name, type, value) => {},
on: (requestCompleted, cb) => cb('rowCount', 'more')
}))
}))